Stopped bullet

[Akbushape]

Have to wonder if a pressure trace is going to give any definitive information in regards to s/s of a bullet.
The steep gradient of the graph from the pressure trace at the start seems to indicate a constant and rapid increase in pressure inside the chamber. S/S of the bullet it seems to me could occur even with constant increase in pressure inside the
chamber. AS I understand it the pressure trace works off the
expansion of the barrel and I doubt whether there is going to be
a measurable change in expansion that will be detectable in the
graph given the steep gradient change at the start. I certainly could be wrong on this.
I believe proof of existence or lack thereof of s/s would have to be done some way other than with a pressure trace.
,This is not to say the pressure trace is a useless piece of
equipment, as it would be interesting to see what the difference
in peak pressure is when testing different powders, bullet
weights, bullet seating depths etc.)

 

[glo]

Seeing that the graph seems to start at about 10,000psi then corrilating that with the beginig of the yeild point, therefore measureable data is a good observation. I don't think that graph was a good reperesentation of how sensitive the equipment is. But, I'll check with the company. I also checked this web site http://www.shootingsoftware.com/pressure.htm . It shows some graphs starting at 0psi.

Personally I think this whole S/S is urban legend. Just go to the RSI website linked above and you can see with your own eyes the S/S isn't there but the slow powder/ light bullet effect is. It's the 6th graph down and has this written about the pressure curve next to the graph: “scary light bullet load recommended in several load manuals taken from a .223 bolt action rifle.” The 4th graph down is the same phenomenon,my opinion) for a 7mm STW, Nosler factory load. [Read example #2, my post #17, this thread for the reasoning behind the light bullet/slow powder event.]

I can only guess but I think this notion of S/S came from shooters experiencing squib loads. The primer goes off and the bullet gets firmly seated into the lands. I've experiences this several times over the last 30 some years of reloading.

I guess and it's a wild one, is that the “shooter” believes because of his observation that if the primer can jam the bullet up into the lands then maybe during normal firing this same thing happens. Then the powder begins burn and thats what restarts the bullet down the barrel. The next thing that shooter is doing, is asking for the scientific proof that it isn't happening.

I think this myth is “busted” before we have even started. My opinion of course. If I read gunsandgunsmithing's post #4 correctly, he is agreeing with Preacher,post #2) that in fact a bullet dose not S/S and has the proof from the Pressure Trace equipment already. I concur with both Guns and Preacher.

But I'm still going to see if I can get the wife to “approve” my new project. Besides she has been interested in the Thompson/Center, Encore Rifle System anyway. I think this would be the perfect platform in which to conduct such experimentation.

 

[glo]

I read the article from the snipercountry link at post #5, this thread, from DickE. I disagree with the the interpretation of Mr. Mike Rock when he worked for the Army.,For disclosure proposes I was a Marine). I would bet if the equipment were sensitive enough and you move into the trillionth of a second measurements there would be detectable movement of the bullet during this start and stop-and start and stop-and start and maybe even stop again event.

I am very dubious of the use of thermal imaging for the proposes of interpreting bullet movement. I have never heard of an inferred camera capable of such sensitivity. It all reeks of d/t^3 and a self serving, governmental agendas.

NOTE: If that inferred imaging camera or processes was classified work,then and now), then Mr. Rock is giving out classified information to the public. Again I am dubious of Mr. Rock's claims. Besides what did that paragraph have to do with bore brake-in? What was the motive of the author to include this non-sequitur?It all sounds like the author was trying real hard to embellish on the credentials of his interviewees. Something smells fishy here.

 

[Akbushape]

Hate to say it but I'm still not convinced one way or the other.
Glo, if you get your pressure trace going please follow up with
a thread on your experiments.
DickE thanks for getting this discussion going and if anyone has any further web sites or information regarding this please share it.

 

[Akbushape]

Glo, went back and studied the graphs that are shown in the
website you mentioned in post #23.
With the time frame involved from primer detonation to the bullet exiting the barrel I agree it is hard to imagine a bullet
coming to a complete stop,as preacher, guns and yourself have
said all along). It just doesn't seem like enough time for the
molecules to stop moving.
As you say the graph depicting the 7mm with factory loads is down right scary. The lines at the start of this graph depicts something different happening when compared with the same spot in time,0 to about .1 miliseconds) in the other graphs,excluding the 12 guage). The other rifles start out around 10,000 to 12,000 PSI. The 7mm starts out between 0 and 5,000 PSI. I don't know what is happening there but something different is going on. I'm not going to suggest bullet S/S but
such slow build-up could indicate an early bullet movement all
or part way out of the neck.,It may be attributal to other factors).Then it gets scary at about 1.2 miliseconds.
I think a lot of us, myself included, take it for granted that
factory loads are surely safe loads,,not the most accurate but
certainly safe). After all, no manufactor would want to risk
a law suit if a gun blows up. However, this 7mm graph demonstrates the fallacy in that assumption. The 223 is
an almost identical situation, except it makes me wonder about
some of the published data in the reloading manuals. In the future if i'm loading light bullets I'll be trying out the faster burning powders listed.
The Pressure Trace II is an amazing little invention and as
soon as I can afford one I'm going to add it to my equipment
inventory. With it and a chrony a person can tell about everything you need to know about a given round's performance.

 

[glo]

Akubshape, I think you have a pretty good working knowledge of what is now going on. You still may not be convinced one way or the other. But that’s okay.

The article cited by DickE as it pertained to the S/S phenomenon was grossly in adequate to state at the end of a paragraph: “This is fact.” But I would like to say this, if in fact a bullet dose state and stop it would have to be in proportion to the time it starts and stops. Otherwise you are violating both the first and second laws of motion. In fact,pun intended) the first thing you must satisfy is the first law. That is, in order to get the bullet moving just the least amount, you must first over come the bullets inertia at rest. The bullets inertia can be calculated as bullet weight time 1 foot per second squared. This will yield the minimum foot-pound force,energy) need the get the bullet moving. So here is an example of why you can’t move the bullet in increments of billionths of seconds.

Here is an example: Increments of Billionths Increments of One
Start and Stop time) 1 billionth of a second. 1 second
Distance traveled) 10 thousandths of an inch. 1 foot
Bullet weight) 95 grains 95 grains
Bullet velocity) 15 hundred thousandths of a ft/s 1 ft/s
Foot-pounds force) .00000005ft-lbf .0002ft-lbf

Because .00000005 does not equal .0002 the first law is violated and the bullet dose not move.

This has been a great discussion. I learned a lot myself.
G

 

[DickE]

Thanks guys, I appreciate all the input from all of you, especially the ones who actually did some math, and research. Debate and discussion is how we learn. But sometimes I wonder about people who always have all the answers, why they never ask any questions.